13,338 research outputs found

    Gaining clinical wisdom from adversity: Nurse leaders’ ethical conflict and resilience experiences

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    Developing effective nurse leaders in today’s“reengineered” corporate healthcare cultures requires that more attention be given to the preparation of ethical leadership during undergraduate programs and nurses’ formative years in practice. Through analyzing the experiences of three nurse leaders dealing with ethical conflicts and the meaning they made of these experiences, we identified that nurses need practical guidance to successfully negotiate ethical conflicts, take risks to uphold their ethical codes, and foster collaborative relationships. According to these nurse leaders, it was important to mentor student and novice nurses in working through workplace ethical conflicts and help guide them through the formulation of successful practical strategies. Our findings showed that these nurses developed resilience and clinical wisdom which they carried through to their leadership practice and future situations

    The Singularity in Generic Gravitational Collapse Is Spacelike, Local, and Oscillatory

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    A longstanding conjecture by Belinskii, Khalatnikov, and Lifshitz that the singularity in generic gravitational collapse is spacelike, local, and oscillatory is explored analytically and numerically in spatially inhomogeneous cosmological spacetimes. With a convenient choice of variables, it can be seen analytically how nonlinear terms in Einstein's equations control the approach to the singularity and cause oscillatory behavior. The analytic picture requires the drastic assumption that each spatial point evolves toward the singularity as an independent spatially homogeneous universe. In every case, detailed numerical simulations of the full Einstein evolution equations support this assumption.Comment: 7 pages includes 4 figures. Uses Revtex and psfig. Received "honorable mention" in 1998 Gravity Research Foundation essay contest. Submitted to Mod. Phys. Lett.

    Slope Stabilization Measures for Kirkwood Penstock, Early Intake, California

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    Kirkwood Penstock, located in a deep, steep-sided canyon near .Yosemite National Park, California, is an integral part of the Hetch Hetchy system, which conveys water from the Sierra Nevada Mountains to the city of San Francisco, California. A heavy rainfall approximately 17 years following construction of the facility triggered settlement of the foundation. Measures undertaken to arrest this settlement included consolidation grouting, construction of facilities to divert surface runoff away from the penstock, and installation of a geomembrane to prevent infiltration of rainfall and snow melt in the vicinity of the penstock. No evidence of further settlement has been detected since completion of the remedial work

    Manufacture of Gowdy spacetimes with spikes

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    In numerical studies of Gowdy spacetimes evidence has been found for the development of localized features (spikes) involving large gradients near the singularity. The rigorous mathematical results available up to now did not cover this kind of situation. In this work we show the existence of large classes of Gowdy spacetimes exhibiting features of the kind discovered numerically. These spacetimes are constructed by applying certain transformations to previously known spacetimes without spikes. It is possible to control the behaviour of the Kretschmann scalar near the singularity in detail. This curvature invariant is found to blow up in a way which is non-uniform near the spike in some cases. When this happens it demonstrates that the spike is a geometrically invariant feature and not an artefact of the choice of variables used to parametrize the metric. We also identify another class of spikes which are artefacts. The spikes produced by our method are compared with the results of numerical and heuristic analyses of the same situation.Comment: 25 page

    Suppression of Dynamic Stall by Steady and Pulsed Upper-Surface Blowing

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    The Boeing-Vertol VR-7 airfoil was experimentally studied with steady and pulsed upper-surface blowing for sinusoidal pitching oscillations described by alpha = alpha(sub m) + 10 deg sin(omega t). The tests were conducted in the U.S. Army Aeroflightdynamics Directorate's Water Tunnel at NASA Ames Research Center. The experiment was performed at a Reynolds number of 100,000. Pitch oscillations with alpha(sub m) = 10 deg and 15 deg and with reduced frequencies ranging from k = 0.005 to 0.15 were examined. Blowing conditions ranged from C(sub mu) = 0.03 to 0.66 and F(+) = 0 to 3. Unsteady lift, drag, and pitching-moment loads were measured, and fluorescent-dye flow visualizations were obtained. Steady, upper-surface blowing was found to be capable of trapping a separation bubble near the leading edge during a portion of the airfoil's upward rotation. When this occurred, the lift was increased significantly and stall was averted. In all cases, steady blowing reduced the hysteresis amplitudes present in the loads and produced a large thrust force. The benefits of steady blowing diminished as the reduced frequency and mean angle of oscillation increased. Pulsed blowing showed only marginal benefits for the conditions tested. The greatest gains from pulsed blowing were achieved at F(+) = 0.9

    High-Q nested resonator in an actively stabilized optomechanical cavity

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    Experiments involving micro- and nanomechanical resonators need to be carefully designed to reduce mechanical environmental noise. A small scale on-chip approach is to add an additional resonator to the system as a mechanical low-pass filter. Unfortunately, the inherent low frequency of the low-pass filter causes the system to be easily excited mechanically. Fixating the additional resonator ensures that the resonator itself can not be excited by the environment. This, however, negates the purpose of the low-pass filter. We solve this apparent paradox by applying active feedback to the resonator, thereby minimizing the motion with respect the front mirror of an optomechanical cavity. Not only does this method actively stabilize the cavity length, but it also retains the on-chip vibration isolation.Comment: Minor adjustments mad

    Synthesis of Chiral Nonracemic Tertiary α-Thio and α-Sulfonyl Acetic Esters via SN2 Reactions of Tertiary Mesylates

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    Syntheses of enantioenriched sulfides and sulfones via substitution of tertiary mesylate with thiolate nucleophile were achieved with modest to excellent success

    Foundation Grouting for the Forks of Butte Powerhouse

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    Construction of a powerhouse on unconsolidated landslide debris materials at the edge of a stream channel in a narrow, steep-sided canyon in northern California entailed application of an unusual combination of grouting techniques to protect the foundation during peak flows. These techniques included permeation grouting, displacement grouting, compaction grouting, and controlled hydrofracture grouting

    Detecting Compton Reflection and a Broad Iron Line in MCG-5-23-16 with the Rossi X-ray Timing Explorer

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    We report the detection with the Rossi X-ray Timing Explorer of a Compton reflection signature in the Seyfert galaxy MCG-5-23-16. RXTE also resolves the Fe K-alpha fluorescence line with FWHM ~48,000 km s^{-1}. This measurement provides the first independent confirmation of ASCA detections in Seyfert galaxies of broad Fe K-alpha lines that are thought to be the signature of emission from the inner regions of an accretion disk orbiting a black hole. Under the assumption that reflection arises from an isotropic source located above a neutral accretion disk, and using a theoretical model that accounts for the dependence of the reflected spectrum on inclination angle, we derive a 90% confidence range for the disk inclination of i = 50 to 81 degrees. The large inclination is consistent with that expected from the unified model for MCG-5-23-16 based on its Seyfert 1.9 classification. If we assume that the high-energy cutoff in the incident spectrum lies at energies larger than a few hundred keV, then the equivalent width of the Fe K-alpha line is much larger than predicted for the amount of reflection. This implies either an enhanced iron abundance, a covering factor of reflecting material > 0.5, or a cutoff in the incident spectrum at energies between ~60 and ~200 keV.Comment: Accepted for publication in ApJ, LaTeX. 14 pages including 3 figures, with 1 table as a separate postscript file. Typo corrected in abstrac
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